#ifndef BZF_MD5_H
#define BZF_MD5_H

#include <cstdio>
#include <cstring>
#include <iostream>


// Constants for MD5Transform routine.
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

// a small class for calculating MD5 hashes of strings or byte arrays
// it is not meant to be fast or secure
//
// usage: 1) feed it blocks of uchars with update()
//      2) finalize()
//      3) get hexdigest() string
//      or
//      MD5(std::string).hexdigest()
//
// assumes that char is 8 bit and int is 32 bit
class MD5
{
public:
  typedef unsigned int size_type; // must be 32bit

  ////////////////////////

  // default ctor, just initailize
  MD5()
  {
    init();
  }

  ////////////////////////

  // nifty shortcut ctor, compute MD5 for string and finalize it right away
  MD5(const std::string& text)
  {
    init();
    update(text.c_str(), text.length());
    finalize();
  }

  ////////////////////////

  // MD5 block update operation. Continues an MD5 message-digest
  // operation, processing another message block
  void update(const unsigned char *input, size_type length)
  {
    // compute number of bytes mod 64
    size_type index = count[0] / 8 % blocksize;

    // Update number of bits
    if ((count[0] += (length << 3)) < (length << 3))
      count[1]++;
    count[1] += (length >> 29);

    // number of bytes we need to fill in buffer
    size_type firstpart = 64 - index;

    size_type i;

    // transform as many times as possible.
    if (length >= firstpart)
    {
      // fill buffer first, transform
      memcpy(&buffer[index], input, firstpart);
      transform(buffer);

      // transform chunks of blocksize (64 bytes)
      for (i = firstpart; i + blocksize <= length; i += blocksize)
        transform(&input[i]);

      index = 0;
    }
    else
      i = 0;

    // buffer remaining input
    memcpy(&buffer[index], &input[i], length-i);
  }

  ////////////////////////

  // for convenience provide a verson with signed char
  void update(const char *input, size_type length)
  {
    update((const unsigned char*)input, length);
  }

  ////////////////////////

  // MD5 finalization. Ends an MD5 message-digest operation, writing the
  // the message digest and zeroizing the context.
  MD5& finalize()
  {
    static unsigned char padding[64] = {
        0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
    };

    if (!finalized) {
      // Save number of bits
      unsigned char bits[8];
      encode(bits, count, 8);

      // pad out to 56 mod 64.
      size_type index = count[0] / 8 % 64;
      size_type padLen = (index < 56) ? (56 - index) : (120 - index);
      update(padding, padLen);

      // Append length (before padding)
      update(bits, 8);

      // Store state in digest
      encode(digest, state, 16);

      // Zeroize sensitive information.
      memset(buffer, 0, sizeof buffer);
      memset(count, 0, sizeof count);

      finalized=true;
    }

    return *this;
  }

  ////////////////////////

  // return hex representation of digest as string
  std::string hexdigest() const
  {
    if (!finalized)
      return "";

    char buf[33];
    for (int i=0; i<16; i++)
      sprintf(buf+i*2, "%02x", digest[i]);
    buf[32]=0;

    return std::string(buf);
  }

  void get_digest(uint8_t * buf) const
  {
    for (int i=0; i<16; i++) {
      buf[i] = digest[i];
    }
  }

  friend std::ostream& operator<<(std::ostream&, MD5 md5);

private:
  void init()
  {
    finalized=false;

    count[0] = 0;
    count[1] = 0;

    // load magic initialization constants.
    state[0] = 0x67452301;
    state[1] = 0xefcdab89;
    state[2] = 0x98badcfe;
    state[3] = 0x10325476;
  }

  ////////////////////////

  typedef unsigned char uint1; //  8bit
  typedef unsigned int uint4;  // 32bit
  enum {blocksize = 64}; // VC6 won't eat a const static int here

  ////////////////////////

  // apply MD5 algo on a block
  void transform(const uint1 block[blocksize])
  {
    uint4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];
    decode (x, block, blocksize);

    /* Round 1 */
    FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
    FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
    FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
    FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
    FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
    FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
    FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
    FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
    FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
    FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
    FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
    FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
    FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
    FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
    FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
    FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

    /* Round 2 */
    GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
    GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
    GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
    GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
    GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
    GG (d, a, b, c, x[10], S22,  0x2441453); /* 22 */
    GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
    GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
    GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
    GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
    GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
    GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
    GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
    GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
    GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
    GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

    /* Round 3 */
    HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
    HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
    HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
    HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
    HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
    HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
    HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
    HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
    HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
    HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
    HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
    HH (b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */
    HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
    HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
    HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
    HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

    /* Round 4 */
    II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
    II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
    II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
    II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
    II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
    II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
    II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
    II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
    II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
    II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
    II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
    II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
    II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
    II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
    II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
    II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;

    // Zeroize sensitive information.
    memset(x, 0, sizeof x);
  }

  ////////////////////////

  // decodes input (unsigned char) into output (uint4). Assumes len is a multiple of 4.
  static void decode(uint4 output[], const uint1 input[], size_type len)
  {
    for (unsigned int i = 0, j = 0; j < len; i++, j += 4)
      output[i] = ((uint4)input[j]) | (((uint4)input[j+1]) << 8) |
          (((uint4)input[j+2]) << 16) | (((uint4)input[j+3]) << 24);
  }

  ////////////////////////

  // encodes input (uint4) into output (unsigned char). Assumes len is
  // a multiple of 4.
  static void encode(uint1 output[], const uint4 input[], size_type len)
  {
    for (size_type i = 0, j = 0; j < len; i++, j += 4) {
      output[j] = input[i] & 0xff;
      output[j+1] = (input[i] >> 8) & 0xff;
      output[j+2] = (input[i] >> 16) & 0xff;
      output[j+3] = (input[i] >> 24) & 0xff;
    }
  }

  ////////////////////////

  bool finalized;
  uint1 buffer[blocksize]; // bytes that didn't fit in last 64 byte chunk
  uint4 count[2];   // 64bit counter for number of bits (lo, hi)
  uint4 state[4];   // digest so far
  uint1 digest[16]; // the result

  // low level logic operations
  static inline uint4 F(uint4 x, uint4 y, uint4 z){
    return (x&y) | (~x&z);
  };
  static inline uint4 G(uint4 x, uint4 y, uint4 z){
    return (x&z) | (y&~z);
  };
  static inline uint4 H(uint4 x, uint4 y, uint4 z){
    return x^y^z;
  };
  static inline uint4 I(uint4 x, uint4 y, uint4 z){
    return y ^ (x | ~z);
  };
  static inline uint4 rotate_left(uint4 x, int n){
    return (x << n) | (x >> (32-n));
  };
  static inline void FF(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac){
    a = rotate_left(a+ F(b,c,d) + x + ac, s) + b;
  };
  static inline void GG(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac){
    a = rotate_left(a + G(b,c,d) + x + ac, s) + b;
  };
  static inline void HH(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac){
    a = rotate_left(a + H(b,c,d) + x + ac, s) + b;
  };
  static inline void II(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac){
    a = rotate_left(a + I(b,c,d) + x + ac, s) + b;
  };
};

#endif